Transglutaminase-catalyzed transamidation:: A novel mechanism for Rac1 activation by 5-hydroxytryptamine2A receptor stimulation
Transglutaminase-catalyzed transamidation:: A novel mechanism for Rac1 activation by 5-hydroxytryptamine2A receptor stimulation
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DOI：
10.1124/jpet.107.135046
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发表时间：
2008-07-01
影响因子：
3.5
通讯作者：
Muma, N. A.
中科院分区：
文献类型：
--
作者：
Dai, Y.;Dudek, N. L.;Muma, N. A.
转谷氨酰胺酶（TGase）通过5-羟色胺（HT）（2A）受体信号传导诱导小G蛋白活化导致血小板聚集（Cell 115: 851-862, 2003）。我们假设刺激神经元中的5-HT2A受体激活TGase，导致5-羟色胺转化为小G蛋白Rac1，从而构成性激活Rac1。通过免疫沉淀和免疫印迹，我们发现，在大鼠皮层细胞系A1A1v中，血清素增加了tgase催化的Rac1的转氨化。这种转酰胺作用发生在未分化细胞和已分化细胞中。使用5-HT2A/2C受体激动剂2,5-二甲氧基-4-碘安非他明治疗，而不使用5-HT1A受体激动剂5-羟基-2-二丙胺四氢萘，可以增加TGase对Rac1的转酰胺作用。在A1A1v细胞中，5-HT2A受体介导了转酰胺反应，因为5-HT2C受体的表达未检测到，而选择性5-HT2A受体拮抗剂阻断了转酰胺反应。时间过程研究表明，在5和15分钟的血清素治疗后，Rac1的转氨化显著升高，但在30分钟后恢复到控制水平。在5 -羟色胺刺激后，Rac1的活性也会短暂增加。半胱胺或小干扰RNA抑制TGase可减少TGase对Rac1的修饰，半胱胺也可阻止Rac1的激活。5-HT2A受体刺激后，5-羟色胺本身通过TGase与Rac1结合，共免疫沉淀实验证明了这一点，半胱胺对5-羟色胺相关的Rac1有剂量依赖性降低。这些数据支持了一种假设，即通过刺激5-HT2A受体，tgase催化5-羟色胺转化为Rac1，从而使Rac1活性短暂增加。通过TGase激活Rac1是神经元中5-HT2A受体信号级联的一种新的效应物和第二信使。
Transglutaminase (TGase)-induced activation of small G proteins via 5-hydroxytryptamine(HT)(2A) receptor signaling leads to platelet aggregation (Cell 115: 851-862, 2003). We hypothesize that stimulation of 5-HT2A receptors in neurons activates TGase, resulting in transamidation of serotonin to a small G protein, Rac1, thereby constitutively activating Rac1. Using immunoprecipitation and immunoblotting, we show that, in rat cortical cell line A1A1v, serotonin increases TGase-catalyzed transamidation of Rac1. This transamidation occurs in both undifferentiated and differentiated cells. Treatment with a 5-HT2A/2C receptor agonist 2,5-dimethoxy-4-iodoamphetamine, but not the 5-HT1A receptor agonist 5-hydroxy-2-dipropylamino tetralin, increases transamidation of Rac1 by TGase. In A1A1v cells, 5-HT2A receptors mediate the transamidation reaction because expression of 5-HT2C receptors was not detectable and the selective 5-HT2A receptor antagonist blocked transamidation. Time course studies demonstrate that transamidation of Rac1 is significantly elevated after 5 and 15 min of serotonin treatment, but returns it to control levels after 30 min. The activity of Rac1 is also transiently increased following serotonin stimulation. Inhibition of TGase by cystamine or small interfering RNA reduces TGase modification of Rac1, and cystamine also prevents Rac1 activation. Serotonin itself is bound to Rac1 by TGase following 5-HT2A receptor stimulation as demonstrated by coimmunoprecipitation experiments and a dose-dependent decrease of serotonin-associated Rac1 by cystamine. These data support the hypothesis that Rac1 activity is transiently increased due to TGase-catalyzed transamidation of serotonin to Rac1 via stimulation of 5-HT2A receptors. Activation of Rac1 via TGase is a novel effector and second messenger of the 5-HT2A receptor-signaling cascade in neurons.